THE STEM AND THE LEAF 



61 



Climbers are, however, quite generally distributed, and many 

 are familiar plants of our own flora. They may be roughly 

 classed into (1) scramblers, (2) root climbers, (3) twiners, 

 and (4) tendril climbers. 



Scramblers sprawl among and over the tops of bushes and 

 thickets. Examples are some kinds of asparagus, our common 

 climbing rose, and cleavers (Gralium Aparine). 



FIG. 48. Woodbine or Virginia creeper, a tendril climber 

 Reduced 



Twiners raise themselves by winding the stem about any slen- 

 der upright support that offers itself. Well-known examples 

 are pole beans, morning-glories, and the hop. The details of the 

 process by which twiners wind themselves about a supporting 

 object cannot be very briefly stated. If carefully watched, 

 the growing tip of the shoot will often be found to describe 

 revolving movements like those of the hands of a watch. When 

 the movement is arrested by contact of the shoot with an ob- 

 ject not too large for the climber to twine about, the resistance 

 which the young moving stem encounters causes it to wind 

 permanently around the resisting object (Fig. 47). Usually 

 the direction of the coils for any given plant is the same. 



